It has been practice in various technical fields to move a member between two different positions when so required as is well known. Apparatus for moving a member between two different positions include, for example, surveillance or monitoring camera apparatus disclosed in the publications of JP-A No. 1999-239356 and JP-A No. 2000-162665. These monitoring camera apparatus comprise a CCD or like solid image pickup device and are adapted for use in a color mode or black-and-white mode. An infrared ray cutting-off filter is disposed or installed in position between the image pickup device and a condenser lens in the color mode. A dummy filter (dummy glass) is disposed between these components in the black-and-white mode. The infrared ray cutting-off filter and the dummy filter are fixedly mounted on a common member, which is moved by the operation of a motor and a slide mechanism for a changeover from one filter to the other.
Such an apparatus has the likelihood that the member fixedly provided with the filters will be stopped in the course of a movement when the load on the motor increases owing to the ingress of dust into the apparatus or when the torque of the motor reduces owing to an accident. Accordingly, widely performed is a control method comprising automatically judging whether the movement is faulty, i.e., whether the member is brought to the desired position, and driving the motor again based on the result of judgment to position the member reliably as desired. The member is detected using a sensor device, such as a microswitch or photointerrupter, for producing an output in the two patterns of Hi and Low. In the case of the monitoring camera apparatus described, it is desirable to provide the sensor device in each of two positions so as to reliably detect the infrared ray cutting-off filter or dummy filter as installed in the desired position. Stated more specifically, it is desired to provide a microswitch for contact with the member, with the infrared ray cutting-off filter disposed between the image pickup device and the condenser lens, and another microswitch for contact with the member, with the dummy filter disposed between these components.
With precision apparatus such as cameras, however, it is generally difficult to provide two sensor devices such as microswitches because of demands for compacted apparatus and the limitations involved in design. Although the publication of JP-A No. 2000-162665 discloses a monitoring camera apparatus wherein one photointerrupter is used as the sensor device for detecting the position of the member, it is not always possible to use the photointerrupter as in the case of the disclosed monitoring apparatus in view of the construction of the apparatus. In moving a member between two different positions, it is therefore desired to use only one sensor device, especially one sensor device of the contact type, for automatically detecting a faulty movement of the member to control the movement of the member to the desired position.
The present invention is intended to overcome the foregoing problems and to provide movement control system and method for controlling the movement of a member between two different positions by automatically detecting a faulty movement of the member with use of a single sensor device so as to move the member to the desired position.